Heat exchanger

ABSTRACT

A heat exchanger includes a shell; a pair of tube plates provided at both ends of the shell; a plurality of heat transfer tubes supported by the tube plates and housed in the shell; and a high-temperature fluid inlet connection for introducing a high-temperature fluid into the shell. A cooling jacket having a porous structure, over which a cooling fluid is to be spread, is provided on the interior surface of the high-temperature fluid inlet connection.

FIELD

Embodiments described herein relate generally to a heat exchanger foruse in a nuclear power plant or a thermal power plant.

BACKGROUND

FIG. 6 is a cross-sectional diagram of a heat exchanger for use in apower plant, illustrating a joint portion between the main body of theheat exchanger and a high-temperature pipe for heating steam. In FIG. 6,reference numeral 60 denotes the shell of the heat exchanger. A largenumber of heat transfer tubes 61, supported by a pair of tube plates 62,are housed in the shell 60. A low-temperature fluid flows through theheat transfer tubes 61. A high-pressure, high-temperature fluid isintroduced from a high-temperature fluid inlet connection 63 into theshell 60. Heat exchange takes place between the high-temperature fluidand the low-temperature fluid flowing through the heat transfer tubes61.

In such a heat exchanger, a thermal stress acts on a region around thejoint between the high-temperature fluid inlet connection 63 and theshell 60. This is because the high-temperature fluid inlet connection 63thermally expands by exposure to a high temperature while the shell 60is kept at a low temperature, and therefore the joint between thehigh-temperature fluid inlet connection 63 and the shell 60 is subjectto a high compressive stress due to simultaneous occurrence of expansionand contraction at the joint. It is, therefore, conventional practice toemploy a thermal sleeve structure in the high-temperature fluid inletconnection 63 to reduce thermal stress.

The above prior art techniques employ a thermal sleeve structure toreduce thermal stress and, in cases where the stress reducing effect isinsufficient, provide an insulating means in the thermal sleevestructure to enhance the effect of reducing thermal stress.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a heat exchanger according to afirst embodiment of the present invention;

FIG. 2 is a cross-sectional view of a variation of the heat exchangeraccording to the first embodiment of the present invention;

FIG. 3 is a cross-sectional view of a heat exchanger according to asecond embodiment of the present invention;

FIG. 4 is a cross-sectional view of a heat exchanger according to athird embodiment of the present invention;

FIG. 5 is a cross-sectional view of a variation of the heat exchangeraccording to the third embodiment of the present invention; and

FIG. 6 is a cross-sectional view of a conventional heat exchanger.

DETAILED DESCRIPTION

Embodiments of the present invention will now be described withreference to the drawings.

A heat exchanger according to the embodiment includes a shell; a pair oftube plates provided at both ends of the shell; a plurality of heattransfer tubes supported by the tube plates and housed in the shell; anda high-temperature fluid inlet connection for introducing ahigh-temperature fluid into the shell. A cooling jacket having a porousstructure, over which a cooling fluid is to be spread, is provided onthe interior surface of the high-temperature fluid inlet connection.

FIG. 1 shows a heat exchanger according to a first embodiment of thepresent invention. The heat exchanger is for use in a nuclear powerplant or a thermal power plant. In FIG. 1, reference numeral 1 denotes ashell constituting the main body of the heat exchanger. A tube plate 2is mounted at each end of the shell 1. A large number of heat transfertubes 3 are supported by the tube plates 2 in the shell 1.

A high-temperature fluid inlet connection 4 is mounted to the shell 1. Ahigh-temperature fluid, which has been fed through not-shownhigh-temperature piping, is introduced from the high-temperature fluidinlet connection 4 into the shell 1. On the other hand, alow-temperature fluid flows through the heat transfer tubes 3. Heatexchange takes place between the high-temperature fluid introduced intothe shell 3 and the low-temperature fluid flowing through the heattransfer tubes 3. The fluid whose temperature has been lowered by theheat exchange is discharged from a fluid outlet connection 5 provided inthe shell 1.

In the heat exchanger of this embodiment, a cooling jacket 6 is mountedon the interior surface of the high-temperature fluid inlet connection4. The cooling jacket 6 is a cylindrical member having a porousstructure with numerous through-holes. The cooling jacket 6 is fit inthe high-temperature fluid inlet connection 4 such that a gap whichallows fluid to flow is formed between the outer surface of the coolingjacket 6 and the interior surface of the seat 4. The lower end of thecooling jacket 6 extends to the joint between the shell 1 and thehigh-temperature fluid inlet connection 4. To the high-temperature fluidinlet connection 4 is mounted a cooling fluid inlet port 7 forintroducing a cooling fluid into the cooling jacket 6. A not-showncooling pipe is connected to the cooling fluid inlet port 7.

The operation of the heat exchanger of this embodiment, having the aboveconstruction, will now be described.

The high-pressure, high-temperature fluid flows from thehigh-temperature fluid inlet connection 4 into the shell 1. Thehigh-temperature fluid inlet connection 4 thermally expands due to itsexposure to the high-temperature fluid. On the other hand, thetemperature of the shell 1 is relatively low because of heat exchangetaking place within the shell 1 between the low-temperature fluidflowing through the large number of heat transfer tubes 3 and thehigh-temperature fluid.

Under such thermal conditions, the cooling fluid is introduced from thecooling fluid inlet port 7 into the cooling jacket 6 provided in thehigh-temperature fluid inlet connection 4. Because the cooling jacket 6has a porous structure with numerous through-holes, the cooling fluid isspouted out by way of the through-holes so as to be covered with thecooling fluid, whereby a increase of the temperature of the interiorsurface of the high-temperature fluid inlet connection 4, which is incontact with the cooling jacket 6, can be controlled.

This can reduce the temperature difference between the high-temperaturefluid inlet connection 4 and the shell 1 at the joint between them,thereby reducing thermal stress. Furthermore, unlike the conventionalthermal sleeve structure that reduces thermal stress mechanically, thecooling jacket 6 can sufficiently respond to the recent movement towardhigher temperature of the high-temperature fluid, making it possible toenhance the structural soundness and the reliability of the heatexchanger.

FIG. 2 shows a variation of the heat changer of this embodiment. In thevariation, the cooling fluid inlet port 7 for introducing a coolingfluid into the cooling jacket 6 is mounted to the shell 1. The coolingjacket 6 has an extension portion 6 a, extending along the interiorsurface of the shell 1 and reaching to the cooling fluid inlet port 7,so that the cooling fluid, introduced from the cooling fluid inlet port7, passes through the extension portion 6 a and spreads over the entirecooling jacket 6. The other construction of the heat exchanger is thesame as the embodiment shown in FIG. 1, and hence the same referencenumerals are used for the same components and a detailed descriptionthereof is omitted.

According to the embodiment of FIG. 2, the cooling fluid is supplied tothe cooling jacket 6 from the cooling fluid inlet port 7 provided in theshell 1. Therefore, a wider area of the heat exchanger, including thejoint between the high-temperature fluid inlet connection 4 and theshell 1, can be cooled with the cooling fluid. This can achieve a higherthermal stress reducing effect.

Though in the embodiments of FIGS. 1 and 2 the cooling fluid is suppliedto the cooling jacket 6 from the not-shown cooling pipe, it is alsopossible to recycle the fluid, whose temperature has been lowered by theheat exchange within the shell 1 and which has been discharged from theshell 1 through the fluid outlet connection 5, to the cooling fluidinlet port 7.

FIG. 3 shows a heat exchanger according to a second embodiment of thepresent invention. Instead of the cooling jacket 6 of the firstembodiment, the second embodiment employs a dome-shaped portion 10formed on the shell 1.

The dome-shaped portion 10 bulges out of the shell 1 and intervenesbetween the shell 1 and the high-temperature fluid inlet connection 4.

In the second embodiment, the high-temperature fluid inlet connection 4is not directly connected to the shell 1, but is separated by thedome-shaped portion 10. This enables reduction of thermal stress asfollows.

In comparison of the case where the high-temperature fluid inletconnection 4 is mounted to the dome-shaped portion 10 according to thesecond embodiment with the conventional case where the high-temperaturefluid inlet connection 4 is mounted directly to the shell 1, in theformer case the high-temperature fluid inlet connection 4 is mounted tothe dome-shaped portion 10 whose diameter is considerably smaller thanthe diameter of the shell 1. Accordingly, the allowable stress,determined by the calculation of pressure capacity, is higher in theformer case according to the second embodiment than in the conventionalcase.

Further in view of the fact that the dome-shaped portion 10 itself has ahigh pressure capacity and a high allowable stress, the secondembodiment of the present invention is expected to have a higher thermalstress reducing effect compared to the conventional case where thehigh-temperature fluid inlet seat 4 is mounted directly to the shell 1.

It is possible to use a thermal sleeve structure in the joint betweenthe high-temperature fluid inlet connection 4 and the dome-shapedportion 10. In this case, the thermal sleeve has the effect of reducingthermal stress at the joint between the high-temperature fluid inletconnection 4 and the dome-shaped portion 10 and at the joint between thedome-shaped portion 10 and the shell 1, making it possible to deal withhigher temperature conditions.

FIG. 4 shows a heat exchanger according to a third embodiment of thepresent invention. The third embodiment employs the cooling jacket 6 ofFIG. 1 and the dome-shaped portion 10 of FIG. 3 in combination. The samereference numerals are used for the same components as in the precedingembodiments, and a detailed description thereof is omitted.

As in the second embodiment shown in FIG. 3, the dome-shaped portion 10intervenes between the shell 1 and the high-temperature fluid inletconnection 4. As in the first embodiment, the cooling jacket 6 ismounted in the high-temperature fluid inlet connection 4. The coolingfluid inlet port 7 for introducing a cooling fluid into the coolingjacket 6 is mounted to the high-temperature fluid inlet connection 4.

According to this embodiment, thermal stress can be effectively reducedby the synergistic effect of the forced cooling by the cooling jacket 6and the high allowable stress of the dome-shaped portion 10.

FIG. 5 shows an embodiment which corresponds to the combination of theembodiment of FIG. 2 and the embodiment of FIG. 3.

In this embodiment the cooling jacket 6 has a shape conforming to theinterior surfaces of the high-temperature fluid inlet connection 4 andthe dome-shaped portion 10, and has an extension portion 6 a extendingto the shell 1. The cooling fluid inlet port 7 is mounted to the shell1.

According to this embodiment, thermal stress can be reduced moreeffectively by the synergistic effect of the extended forced cooling bythe cooling jacket 6 and the high allowable stress of the dome-shapedportion 10.

Though in the embodiments of FIGS. 4 and 5 the cooling fluid is suppliedto the cooling jacket 6 from the not-shown cooling pipe, it is alsopossible to recycle the fluid, whose temperature has been lowered by theheat exchange within the shell 1 and which has been discharged from theshell 1 through the fluid outlet connection 5, to the cooling fluidinlet port 7.

While the embodiments have been described, it will be understood bythose skilled in the art that the present invention is not limited tothe particular embodiments described above. For example, instead of thedome-shaped portion 10, it is possible to use, for example, a sphericalor conical intervening portion insofar as it can achieve separation of ahigh-temperature area and a low-temperature area.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel methods and systems describedherein may be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the methods andsystems described herein may be made without departing from the sprit ofthe inventions. The accompanying claims and their equivalents areintended to cover such forms or modifications as would fall within thescope and sprit of the inventions.

1. A heat exchanger comprising: a shell; a pair of tube plates providedat both ends of the shell; a plurality of heat transfer tubes supportedby the tube plates and housed in the shell; a high-temperature fluidinlet connection for introducing a high-temperature fluid into theshell; and a cooling jacket, over which a cooling fluid is to besupplied, is provided on the interior surface of the high-temperaturefluid inlet connection, wherein the cooling jacket has a porousstructure.
 2. The heat exchanger according to claim 1, wherein a coolingfluid inlet port for introducing the cooling fluid into the coolingjacket is provided in the high-temperature fluid inlet connection. 3.The heat exchanger according to claim 1, wherein the cooling jacket hasan extension portion extending along the interior surface of the shell,and a cooling fluid inlet port for introducing the cooling fluid intothe cooling jacket is provided in the shell.
 4. The heat exchangeraccording to claim 1, wherein a fluid after heat exchange, which hasbeen discharged from the shell through an outlet connection, is recycledand introduced as the cooling fluid into the cooling fluid inlet port.5. The heat exchanger according to claim 1, wherein a thermal sleevestructure is used in the joint between the high-temperature fluid inletconnection and the dome-shaped portion.
 6. A heat exchanger comprising:a shell; a pair of tube plates provided at both ends of the shell; aplurality of heat transfer tubes supported by the tube plates and housedin the shell; and a high-temperature fluid inlet connection forintroducing a high-temperature fluid into the shell; and a dome-shapedportion provided with the shell; wherein the high-temperature fluidinlet connection is connected to the shell via the dome-shaped portion.7. The heat exchanger according to claim 6, wherein a cooling jackethaving a porous structure, over which a cooling fluid is to be spread,is provided on the interior surfaces of the high-temperature fluid inletconnection and the dome-shaped portion.
 8. The heat exchanger accordingto claim 6, wherein a cooling fluid inlet port for introducing thecooling fluid into the cooling jacket is provided in thehigh-temperature fluid inlet connection.
 9. The heat exchanger accordingto claim 7, wherein the cooling jacket has an extension portionextending along the interior surface of the shell, and a cooling fluidinlet port for introducing the cooling fluid into the cooling jacket isprovided in the shell.
 10. The heat exchanger according to claim 9,wherein a fluid after heat exchange, which has been discharged from theshell through an outlet connection, is recycled and introduced as thecooling fluid into the cooling fluid inlet port.
 11. The heat exchangeraccording to claim 6, wherein a thermal sleeve structure is used in thejoint between the high-temperature fluid inlet connection and thedome-shaped portion.